It is true that you can use the LSD unit from the rear end of the Audi V8Q. This is a torsen type LSD. You will need the LSD and drive shaft flanges from the V8Q. There is also a little machining that needs to be performed on one side of the diff and the flanges have to be redrilled for the Porsche bolt pattern. Supposedly it works well if you want to use this type of diff. Reports are out there that these units are going for around 100 bucks which means that are practically free. If I didn't have my heart set on a clutch type diff I would give this one a try. Here's a link to get you some more info if you need it.

http://www.924board.org/viewtopic.php?t=23820